Screw-extractor.



J. O. ROBERTS SCREW EXTRAGTOR. APPLICATION FILED MAKE-1, 1012.

1,105,535. Patented July 28, 1914.

c. u @hzweumf Qzm WZJW i T FFIQE.

JULIUS O. ROBERTS, OF SALINA, KANSAS.

SCREW-EXTRACTOR.

mosses.

,a citizen of the United States of America,

and a resident of Salina, county of Saline, and State of Kansas, have invented certain new and useful Improvements in Screw-Extractors, of which the following isa specification.

My invention relates to screw extractors and, has for its object improvements in devices of that character.

More specifically, the object is to provide an instrument for the removal of screws which have been broken or have lost their heads and cannot be removed by ordinary means.

In the accompanying drawings Figure 1 is a section showing the device applied to the extraction of a set screw which has had its head twisted off; and Fig. 2 is a section online 22 of Fig. 1.

In the said drawings, A is a set screw embedded in the metal B, and C is a hole drilled in the center of the screw for the insertion of the instrument.

The body part D is preferably square for the purpose of permitting a wrench to be applied to it, and extending downward from the body is a tapered portion E which is given a twist very similar to that of a twistdrill. For the extraction of right-hand screws, the taper part is given a left-hand twist, and for the extraction of left-hand screws the tapered part would have a righthand twist.

The hole C to be drilled in the screw A should be slightly lar er in diameter than the point of the twist but should not be so Specification of Letters Patent.

Application filed March 24, 1913.

Patented July 28, 1914.

Serial No. 758,334.

large as to prevent the twist from wedging in the hole by the point of the tool striking the bottom. lVhen the instrument is inserted in the hole C and turned to the left it locks itself by the corners F biting into the metal of the screw. The result of such turning is, of course, to remove the screw by causing it to turn to the left with the tool.

By making the twist portion tapered the same instrument will operate equally well in holes of different sizes, and the same size of tool will work equally well for the removal of both large and small screws. For the removal of large screws it is of course desirable to have the hole C comparatively large so that the strain will come upon the larger and stronger part of the taper E. For convenience in removing small screws I make the top of the shank square and tapered as shown at H for the application of an ordinary bit brace.

What I claim is A hand tool for extracting broken off screws comprising an operating portion, the latter bearing spiral, edged ribs and being sufliciently tapered to adapt it when the tool is inserted in an opening drilled in the screw to be removed, to bite into the walls of such opening when the tool is turned in the direction necessary to unscrew said screw, to thei'eby cause said screw to turn with said too Signed at Salina, Kansas this 20 day of March 1913.

JULIUS O. ROBERTS. Witnesses:

E. L. Winona, B. O. WILDER. 

